Biomedical subjects

D G Mou

Publications and source records attributed to D G Mou.

6 recordsLinked to original sources

PubMed1992

Synthesis of hydrolytic enzymes during production of tylosin by Streptomyces fradiae.

The exposure of a wild-type tylosin producing strain of Streptomyces fradiae to mutagenic agents resulted in the isolation of several tylosin over-producing strains. Examination of three mutants, T4310, 612 and 3204 showed that improved tylosin production was associated with increased hydrolytic enzyme activity and cell growth. The wild-type strain showed lower levels of hydrolytic activity including, protease, amylase, lipase and esterase activities and attained a lower cell density than the mutants.

Amylases↗

PubMed1992

High-density Escherichia coli cultivation process for hyperexpression of recombinant porcine growth hormone.

Fermentation studies were performed on an Escherichia coli culture that carries a recombinant plasmid composed of an ampicillin-resistant gene, a temperature-regulated pL promoter, and a porcine pituitary cDNA sequence coding for growth hormone. The objective was to achieve high cell density while maintaining the specific expression level of recombinant porcine growth hormone (r-pGH) observed in shake flasks. At a specific expression level of 20% of total cell protein, the cell density of a glucose-limited fed-batch process reached 38 units of OD600 in 14 h, compared to flask cultivation, which resulted in only 1.4 units of OD600 in the same period. The observed critical fermentation conditions for maximal expression included (1) limiting glucose concentration below 1 g l-1 throughout the fed-batch growth and induction phases, (2) keeping postinduction temperature at 42 degrees C for 5-7 h, and (3) maintaining a postinduction growth rate around 0.17-0.21 h-1.

Animals↗

PubMed1991

Study of high density Escherichia coli fermentation for production of porcine somatotropin protein.

Recombinant E. coli strains and culture conditions were studied for the fermentation expression of porcine somatotropin (PST) inclusion bodies under the control of a pL promoter. Our objective was to achieve high cell density together with a high level of recombinant protein expression. Improved fermentation conditions included oxygen enrichment, yeast extract (YE) effect, optimal specific growth to switch on gene expression, and feeding strategies. To maintain a low residual glucose concentration, a medium feed rate was controlled on a real-time basis by using cell density information estimated from on-line carbon dioxide monitoring of a fermentor's exhaust gas. The optimal specific growth rate required to initiate a temperature shift in our system was found to be around 0.2 hr-1. The cell density and PST expression level could reach 55 OD600 and 35%, respectively, after 16 hours of cultivation under optimal conditions by applying computer-controlled nutrient feed. In our recombinant host/vector system, the location of cl gene appears to affect gene expression under YE-supplemented and/or a high cell density culture condition. With cl gene placed on plasmid, our E. coli host no longer showed sensitivity toward YE in PST gene expression.

Animals↗

PubMed1991

Microbial agents for decolorization of dye wastewater.

Colored dye wastewater presents a formidable task for biological treatment. Depending on how it is generated, wide pH spans and high salt concentrations such as chloride ion often add to the difficulties. Systematic screening for dye decolorizing and/or degrading bioagents from soil and water samples discovered fungi which show dramatic color removal capability (Shen, et al., 1990). One example shows that up to 99% reduction of light absorption at characteristic wavelength of a red dye (200 mg/L) could be obtained within 48 hours. This ability does not appear to be specific toward dyes targeted for action. It clarifies, often beyond detection by naked eyes, a repertoire of colored wastewater samples. These results appeared to be insensitive to wide variations in pH and salt concentration and, they are not limited to one particular fungal species or genus either upon further investigation. This dye adsorption mechanism may be of great significance in uncovering new methods for bio-removal or bio-recovery of dye substances in wastewater.

Journal Article↗

PubMed1983

Process dynamics, instrumentation and control.

A total of 77 references pertaining to the subject were consulted to compose the present review. In addition to their years of publication (1981-1983), the references were selected primarily for their practicality and ability to provide experimental results and confirmation. First, a generalized model illustrating the biochemical reaction engineering considerations is presented. Here the knowledge of reactor and reaction kinetics is emphasized and the need for process instrumentation identified. Recent developments in key process sensors are then discussed in detail along with their utilities in various process situations. Finally, application of control principles and on-line computers to biochemical process operation is given a realistic evaluation by considering the process dynamics and instrumentation capabilities. Future challenges and opportunities from both the reaction engineering and system engineering points of view are carefully assessed. The most recent review relevant to the subject is that by Bull (1983).

Journal Article↗

PubMed1976

Application of dynamic calorimetry for monitoring fermentation processes.

The rate of heat evolution (kcal/liter-hr) in mycelial fermentations for novobiocin and cellulase production with media containing noncellular solids was measured by an in situ dynamic calorimetric procedure. Thermal data so obtained have proved significant both in monitoring cell concentration during the trophophase (growth phase) and in serving as a physiological variable in the fermentation process. The validity of this technique has been demonstrated by closing the overall material and energy balances. The maintenance energy in a batch fermentation can be calculated by integrating heat evolution data. This integration method is applicable to a fermentation lacking a precise cell growth curve. The maintenance coefficient, obtained for the novobiocin fermentation by Streptomyces niveus, is equal to 0.028 g glucose equivalent/g cell-hr. The production of novobiocin in the idiophase (production phase) also correlates well with the amount of energy catabolized for maintenance and this results in an observed conversion yield of glucose to novobiocin of 11.8 mg of novobiocin produced per gram of glucose catabolized. A new physiological variable, kilocalories of heat evolved per millimole of oxygen consumed, has been proposed to monitor the state of cells during the fermentation. This method may provide a simple way to monitor on-line shifts in the efficiency of cell respiration and changes in growth yields during a microbial process.

Calorimetry↗